The major objective is to develop meaningful concepts and contribute important factual information dealing with the comparative role of brain, spinal, and hormonal mechanisms in sexual behavior and other sexually dimorphic behavioral patterns of mammals. Examples of the types of questions being pursued are function of the medial preoptic-anterior hypothalamic area (as well as other basal forebrain areas) in serving as target tissue for gonadal androgen activation of sexual behavior, and the role of the medial preoptic-anterior hypothalamic area in changes in sociosexual behavior of males at the time of puberty. Laboratory rats, cats, and dogs are used according to which species is most appropriate to the particular problem being investigated. BIBLIOGRAPHIC REFERENCE: Hart, B. L. and Jones, T. O. A. C. 1975. Effects of castration on sexual behavior of tropical male goats. Hormones and Behavior, 6: 247-258.